FIG. 1 depicts an example prior art load control environment 102, such as a room in a residence or an office building. As shown in FIG. 1, the load control environment 102 may include various types of load control devices for controlling an electrical load. The load control devices may include a lighting control device 104 (e.g., a dimmer switch, a ballast, or a light-emitting diode (LED) driver) for directly controlling an amount of power provided from an alternating-current (AC) to an electrical load, such as a lighting load 106, a motorized window treatment 112 for controlling the position of a covering material 114, a thermostat 120 for controlling an HVAC system, and/or a plug-in load control device 122 for controlling an amount of power provided to a floor lamp 124, a table lamp, an appliance, or an electrical load of another device that is plugged in to the plug-in load control device 122. The lighting control device 104, the motorized window treatment 112, the thermostat 120, and/or the plug-in load control device 122 may be two-way communication devices. The lighting control device 104, the motorized window treatment 112, the thermostat 120, and/or the plug-in load control device 122 may be control-target devices that may be capable of receiving and/or implementing control instructions based on load control messages received from one or more control-source devices.
The load control environment 102 may include one or more control-source devices that may transmit load control messages to the control-target devices. The control-source devices may be one-way communication devices. The control-source devices may include a daylight sensor 108, an occupancy sensor 110, a shadow sensor 116 (e.g., a window sensor or a cloudy-day sensor), and/or a remote control device 118. The remote control device 118 may include a wireless switch, a wireless dimmer, a handheld remote control, a keypad, a cellular phone, a tablet, or another wireless remote control device capable of sending a load control message to a control-target device. The load control message from the remote control device 118 may include a user identified command for controlling a control-target device. The daylight sensor 108 may send a load control message to a control-target device based on a detected level of available daylight in the load control environment 102. The occupancy sensor 110 may send a load control message to a control-target device based on detected movement or lack of movement within the load control environment 102. The shadow sensor 116 may send a load control message to a control-target device based on a measured level of light received from outside of the load control environment 102. For example, the shadow sensor 116 may detect when direct sunlight is directly shining into the shadow sensor, is reflected onto the shadow sensor, or is blocked by external means, such as clouds or a building, and may send a message indicating the measured light level. The shadow sensor 116 may be installed at a window level to communicate current exterior light conditions.
A control-target device may control a corresponding electrical load based on the information included within the load control messages received from one or more control-source devices. The lighting control device 104 may increase or decrease the lighting level of the lighting load 106 based on the information received within a load control message. The thermostat 120 may increase or decrease the temperature of the load control environment 102 based on the information received within a load control message. The motorized window treatment 112 may raise or lower the position of the covering material 114 based on the information received within a load control message. The plug-in load control device 122 may turn on and off and/or increase or decrease the power provided to the floor lamp 124, or other device that may be plugged in to the plug-in load control device 122, based on the information received within a load control message.
The control-source device may send the load control message to the control-target device directly or via a system controller 126. The communications between the control-source device and the control-target device may be wireless or wired communications. The load control message may include load control instructions or an indication of a status event from which load control instructions may be determined. The system controller 126 may receive the indication of the status event and may determine load control instructions for being sent to one or more control-target devices. The status event may include a user identified command (e.g., increase or decrease a dimming level of the lighting load 106), a measured light level in the load control environment 102, a detected movement or lack of movement within the load control environment 102, an amount of light directly received from outside of the load control environment 102, or another status event that may be used to control an electrical load.
FIG. 2A depicts an example prior art environment in which multiple load control messages may be transmitted within a wireless range 204. As shown in FIG. 2A, the wireless range 204 may include one or more load control environments 102a, 102b, 102c. The load control environments 102a, 102b, 102c may be included in a building 202. Load control environments 102a and 102b may be on separate floors in the building 202. Load control environments 102a and 102c may be on the same floor in the building 202. Each load control environment 102a, 102b, 102c may include one or more load control devices, such as a lighting control device 104a, 104b, 104c, a daylight sensor 108a, 108b, 108c, an occupancy sensor 110a, 110b, 110c, a motorized window treatment 112a, 112b, 112c, a shadow sensor 116a, 116b, 116c, a thermostat 120a, 120b, 120c, and/or a plug-in load control device 122a, 122b, 122c. 
Multiple load control devices can transmit wireless communications at the same time and on the same channel, which tends to cause interference among load control communications transmitted within the wireless range 204. Some load control devices may transmit load control messages at the same time because the load control messages may be transmitted based on the detection of the same updated status event. For example, when daylight sensors 108a, 108b, 108c or shadow sensors 116a, 116b, 116c detect an increased level of light, each sensor may transmit a load control message. As each sensor may detect an increased level of light at the same time, the load control messages transmitted by multiple sensors tends to be transmitted at the same time and cause interference.
As shown in FIGS. 2A and 2B, multiple load control devices may be transmitting load control communications within the same wireless range 204. The wireless range 204 may include communications from load control devices within one or more of the load control environments 102a, 102b, 102c, communications from other load control environments within the building 202, and/or communications from load control devices in other buildings, such as the building 208 shown in FIG. 2B for example. As the number of wireless communications within the wireless range 204 increases, the interference may also increase causing the number of successful communications to decrease.
Referring again to FIG. 2A, some load control systems use the system controller 206 to coordinate the timing of the transmission of load control messages to avoid interference. The system controller 206 may detect interference among load control messages transmitted within the wireless range 204 and may instruct some load control devices to delay communications to avoid message collision. While two-way communication devices may be capable of receiving transmission delay instructions from the system controller 206, one-way communication devices may be unable to receive the transmission delay instructions. The transmission of these transmission delay instructions within the wireless range 204 may also add to the number of communications being transmitted within the wireless range 204, which may cause additional interference initially.
Some control-source devices may independently determine the timing of the transmission of load control messages to avoid interference. A control-source device may detect other communications that may potentially cause interference. The control-source device may transmit load control messages when the amount of other communications within the wireless range 204 is below a threshold.
Some control-target devices may use the signal strength of received load control messages to filter out interference from load control messages intended for a control-target device. A control-target device may process load control messages that are received with a stronger signal strength over load control messages received with a weaker signal strength. For example, the motorized window treatment 112a may receive a load control message from shadow sensor 116b and may determine the received signal strength of the load control message. While receiving the load control message from the shadow sensor 116b, the motorized window treatment 112a may receive a load control message from the shadow sensor 116a. The signal strength of the load control message from the shadow sensor 116a may be stronger because the shadow sensor 116a may be closer to the motorized window treatment 112a. As a result of the proximity of the shadow sensor 116a to the motorized window treatment 112a, the motorized window treatment 112a will stop receiving the load control message from the shadow sensor 116b and begin receiving and processing the load control message from the shadow sensor 116a. 
Filtering load control messages based on received signal strength may allow a control-target device to filter out interfering messages and receive the load control messages intended for the control-target device. However, the load control messages intended for the control-target device may reach a targeted device with a weaker signal strength than an interfering signal, which may cause the load control messages intended for the control target device to be improperly discarded.